Interlocked electric switch



Oct. 7, 1952 J. BIERENFr-:LD 2,612,789

' INTERLOCKED ELECTRIC SWITCH Filed Jan. e, 195o 5 sheets-sheet 1 un hull Quinny@ i I 55 a@ Oct. 7, 1952 J. BIERENFELD ,2,612,789

INTERLOCKED ELECTRIC SWITCH Filed Jan. 9, 195o l 5 sheets-sheet 2 Oct. 7, 1952 J. BIERENFELD 2,612,789

INTERLOCKED ELECTRIC SWITCH Filed Jan. 9, 1950 5 Sheets-She/et 5 Ad/#fj JQ Q @51.

Oct. 7, 1952 J. BIERENFELD 2,612,789

INTERL'OCKED ELECTRIC SWITCH Filed Jan. 9, 1950 5 Sheets-Sheet 4 Oct. 7, 1952 J. BIERENFELD 2,612,789

INTELOCKED ELECTRIC SWITCH Filed Jan. 9, 1950 I 5 Sheets-Sheet 5 Vu Mm?? Patented Oct. 7, 1952 INTERLOCKED ELECTRIC SWITCH Josef Bierenfeld, Milwaukee, Wis., assignor to Square D Company, Milwaukee, Wis., a corporation of Wisconsin vApplication January 9, 1950, SerialNo. 137,590

(Cl. 'f4-iss) v 9 Claims.

This invention relates broadly to interlock mechanisms and refers more particularly to interlocked electric switches of the type illustrated in Patents Nos. 2,262,071 and 2,363,912 issued to H. L. Van Valkenburg November 11, 1941', and November V28, 1944, respectively.

vAs brought out in the aforesaidv Patent No. 2,262,071 it is desirable in an interlock for a pair of companion switches to assure substantial opening o'f the closed switch before the open switch can be closed. This is especially important in electromagnetically operated switches having relatively short opening and closing strokes.

In the most elementary form of mechanical interlock in which a rocker arm connects the contacter assemblies of the two switches, the contactor assembly of the vswitch being opened travels the same distance per unit of time as the contactor of the switch being closed. The optimum condition is one wherein the closed switch must be fully open before the open switch can begin to close. While the interlock of the aforesaid patents approaches this optimum condition, it is a purpose of the present invention to provide an improved mechanical interlock which not only requiresthe closed switch to be nearly fully opened before the open switch can begin to close, but in which binding or jamming of the mechanism is entirely precluded.

It is also .very important that the interlock mechanism be so designed and constructed that the force imposed thereonby energization of the electrcmagnet of the open switch will not restra-in the closed switch from freelyy dropping open. The possibility of such restraint is an objection to the so-called interfering-bar type of interlock wherein a locking bark slides horizontally to lock out the open switch. In such interlocks the friction between the parts will sometimes prevent the closed switch from opening if the electromagnet of the open switch is energized slightly before that ofthe closed switch is deenergized. f

In recognition of this defect the presentinyvention provides an interlock wherein such binding due to friction is entirely impossible.

It is, therefore, a purpose and object of this invention to provide an improved mechanical interlock especially adapted for interlocking two companion electric switches wherein these desirable advantages are attained with a simple mechanism.

Another object of this invention is to provide a mechanical interlock of the character de- 2. scribed which may be readily appliedwithout change-to a pair ofswitches arranged either side-by-side or in tandom one above the other.

Another object of this invention is to provide an interlock of the character described which may be applied without change to switches of different sizes; and more especially to switches having diierent length strokes. Thus, for instance, the interlock of f this invention can; without change, be used on a switch having a 1% stroke as Well ason a switch having a, 1%" stroke and moreover can be used to interlock switches of such unequal strokes.

A further object of this invention is to provide a mechanical interlock which is rugged and fully capable of withstanding the stresses that may be imposed thereon in effectuating its purpose of preventing simultaneousk closure of two switches.

A still furtherobject of this invention is to provide an interlock which while especially adapted for use with two electromagnetically actuated switches is equally useful for preventing simultaneous movement in one direction of any two movable members.

`With the above and other objects in view, which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood `that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawings illustrate two complete examples of the physical embodiments of the invention constructed according to the best modes so far devised for the practical application of the principles thereof, and in which:

Figure 1 is a front elevational view of two sideby-side electromagnetically actuated switches with the interlock of this invention applied thereto; f

Figure 2 is a top plan view of the contactor assemblies of the switches shown in Figure l and of the interlock applied thereto;

Figure 3 is a front elevational view of the interlock mechanism per se but illustrating the manner in which the device may be applied to two switches smaller than those shown in Figure 1, by merely reducing the length of the switch carried operating arms and the mounting bar upon which the interlock is mounted;

Figure 4 is a front elevational view of two electromagnetically actuated switches arranged in tandem and illustrating the interlock of this invention applied thereto;

Figure 5 is a side view of the tandem arranged switches of Figure 4 and the interlock applied thereto;

Figure 6 is a front elevational view of the interlock perse illustrating' the action thereof;

Figure '7 is a vperspective view of the main elements of the interlock mechanism shown detached from the remainder of the device;

Figure 8 is a diagrammatic view illustrating the action of the interlock; and

Figure 9 is a diagram illustrating the relative travel of the switch contactors in moving to closed and open positions, with the different positions of the contactors indicated by the same indicia employed in Figure 9 to show the different positions of the interlock.

Referring now particularly to the accompanying drawings in which like numerals indicate like parts throughout the sevaral views, the numerals I I and I2 indicate generally two electromagnetically actuated switches `each having a contacter assembly including a yoke 3 constrained to vertical motion and movable `upwardly to close the switch upon energization of its solenoid l5. n f

Simultaneous closure of the two switches is prevented by the interlock of this invention, indicated generally by the numeral I"I. The interlock is mechanical in action and is mounted upon a cross bar I8 xed at its opposite ends to a suitable stationary part of :each switch as, for instance, the solenoidframe.

An operating arm I9 is Xed to the yoke |'3 of each switch or to any other suitable part thereof which is movable with a translating motion along with the contactor assembly fof the switch. These operating arms are identical and, when vboth switches are open, vare directly opposite each other. At this time the entire mechanism lmaybe said to be in neutral'.V

Obviously upon closure of one of the switches its operating arm moves upwardly with the contactor assembly of the closed switch. This upward movement of the lifted operating arm sets the interlock mechanism to secure the other operating arm and consequently the switch contactor assembly to which it is connected against upward switch closing movement, and as will be hereinafter more fully described in this blocking or operative condition of the interlock the then open switch is positively held against closure and cannot begin to close until the closed switch is either fully open or almost fully open. The interlock per se comprises two cooperating stationary and movable elements 2| and A2,2 respectively. The stationary element 2| is a flat guide -plate having two opposite upwardly converging arcuate slots 23 and 24 in its lower portion and two connected substantially arcuate upwardly diverging slots 39 and 3| formed in the upper part thereof. Rollers 25 and 26 carried by the movable element 22 are received in the lower slots 23 and 24 respectively to ride up and ldown therein, and the movable element has a third roller 32 thereon received and movable in the upper slots 30 and 3|.

The movable element 22 consists oftwo identical rocker plates overlying the opposite faces of the guide plate and connected together by the axles 28, 29 and 33 of the rollers 2-5, 26 and 3,2 respectively. Therollers25,` 26 and4 32 operating in their respective slots connect the stationary and movable elements together for relative moverlie :the adjacent inner endportionsof the operating arms I9 and to effectthe necessary connection between the interlock and the two switches, the movable element 22 is connected to each arm by `means of rollers 36 journalled on the axles 28 and 29 and received in elongated slots or openings v35 in the inner end portions of the arms.

To enable -the^interlock mechanism to be applied to switches vof diiferent sizes the operating arms I9 -are provided in maximum lengths to accommodate the largest size switch for which the device is designed and have two endwise spaced roller receiving slots 35 as shown in Figure 1. The horizontal mounting :bar I8, ofcourse, also must be Vlong enoughto span the distance between the switches. Thus to apply thefinter- 'lock to `a pair of smaller switches it is Aonly nec'- essary to provide a shorter mounting bar f|8 and cut oi the operating arms rI9 between their two roller receiving slots as shown in Figure 3. In all other respects the mechanism is the same whether'the switch be two, three orfour pole.

As will .be brought .out hereinafterthe same interlock also can be used to interlock companion switches each of which has a `different length stroke.

The interlock mechanism is also readilyapplicable to installations in which the companion switches are arranged -in tandem one above the other. In this case, as shown in AFigures yland 5, a vertical mounting `bar or plate 31 is substituted for the cross 'b'ar I8. `The upper .and -lowerpends of the plate 31 are secured to suitable stationary portions of the switches. and as .before the `cam plate 2| is securedv to this mounting platel. Different operatingl arms are, 4of course, needed but here again the two arms A38 are identical; one of whichin this case the lower one-is connected directly to the contactor :assembly of the lower switch, while the other is connected to the contactor assembly of the upper switch through an extension arm or link 39.

Since the lower arm 38 and the extension arm or link 39 are pivoted to their respective contactor assemblies, the operating arms may be directly pivoted to the movable element of the inter.- lock.

Whether the switches to which the interlock is l applied are arranged side-by-side or one above the other, the action of the interlock is the same. In each case closure of one switch is accompanied by vrocking movement of the movable element 22 from a neutral position to a blocking position preventing closure of the other switch and vice versa.

Thus, assuming that both switches are open so that the interlock is in neutral, in this condition the rollers 25 and 26 are horizontally opposite each other at the bottoms of their respective arcuate slots 23 and 24. In this condition of the interlock the rollers 25 and 26 provide trunnions engageable with bearing seats provided by the 'bottom portionsof their respective slots to afford two transient pivotal connections between the stationary and movable elements of the -interlock about either one of which the Inova-ble element may fulcrum. To enable this rocking movement, the arc of each slot' 23 and 24 isstgruck v opening;

It is important to observe, however, thatthe only functions of the slots 23 and 24 are to proy yvide bearing seats in their bottom portions for the rollers or trunnions 25 and 26, to preclude lateral shifting of the movable element relative to the stationary element beyond the extent permitted by normal operating clearancesbetween the trunnions 25 and 26 and the edges of their slots, and to cooperate with the roller 32 riding in the upper slots 30V and 3| in guiding the rollers 25 and 26 to their lower pivot forming positions. These functions could be accomplished just as well either bythe inwardly facing concave edges of the slots alone, or by the outwardly facing convex edges of the slots alone. For example, the entire medial portion of the stationary member 2| between the slots 23 and 24 could be cut away to leave only a single large opening having inwardly facing concave edges cooperable with the roller in the upper slots 30 andl 3|A tc guide the rollers 25 yand 26 to pivot forming positions engaging bearing seats at the bottom of the or the opposite side edges of the stationary member 2| could have the metal denning the concave edges of the slots 23 and 2 4 cut away to leave only the inner convex edges thereof to cooperate with the roller 32 in the upper slots 3|l'and 3| in guiding the rollers 25 and 26 to' pivot forming positions at the lower bearing seat ends of the' notches thus formed. Though either expedient would be satisfactory, it is preferable to employ the slots 23 and 24 so that the resulting greater area of surface to surface engagement between the flat movable elements-22 and the flat stationary element 2| therebetween minimizes wear of the parts and assures longer trouble-free operation of the interlock.'

In the absence of the'top'roller 3-2 and the 'slot y SKL-3| in which it rides, and despite the presence of the necessary working clearance between the trunnions 25and 26 and the sides of vtheir slots 23.and 24,' there'would be danger of the trunnions becoming wedged in their slots `by a lifting force applied to one of the trunnions in consequence of energization of its associated switch before the other trunnioncompleted its descentin consequence of deenergization of its associated switch. Under these conditions, the force tending to lift the first mentioned trunnion into the converging portion of its slot can be resolved into a frictional force on the axle of the other trunnion greater than the opening force which can be brought to bear upon it by associated switch when the latter is deenergized.

Although there is clearance betweenthe roller 32 and the edges of the slot 3ll3| in which it rides, liust as there is between the trunnions 25 and 25 and the edges of their slots, and the fact` that the top edges 40 and 4| of the slot 30-3i lie athwart the direction which movement of the roller 32 would have to take during attempted closure of the open switch, this clearance is taken up and further movement of the movable element 22 toward concurrent closure of both switches isl limited and prevented before wedging engagementof both edges of their slots can take place. Hence, the engagement of the roller 32 with the tracks provided by the edges lll-4| effectively prevents jamming of the trunnions between theouter edges of their slots 23-24 which would'occur upon concurrent energization of both switches the contacter of its trunnions with theouter if the roller 32 and the slot Sil-3| in which it rides were not present.

It will be seen, therefore, that the upper edges 43 and 4| of the slots 30 and 3| constitute block'- ing surfaces cooperablefwith the roller 32 to not only limit simultaneous upward movement of the two trunnions 25 and 26 from their fulcruming or neutral positions, but that these edges may also be considered. as cam tracks which, in either lock-out position of the movable element constrain it tor rock to the opposite lock-out or tol neutral position.

In other words, with the switch l2 closed so' that its associated operating arm and the trunnion 26 are in their raised positions, the roller f 32 has been swung counterclockwise about trun- -nion 25 into the outer portion of the slot 33,

and the track portion or edge 40 of this slot coacts with the roller 32 to block such lifting of the trunnion 25 off of its seat as would result in the trunnions becoming wedged' intheir slots, so that the movable element 22 is constrained against any movement other than clockwise rocking motion about the trunnion 25 toward its neutral position.

Hence the switch is effectively locked in its open position as long as the switch |2 remains closed, and until the roller 32 is carried off of the track 40 by the contactor of the switch l2 during opening thereof.

Similarly if the switch is closed so that the movable element of the interlock has been rocked about the transient pivot provided by the engagement of itstrunnion 23 in the bottom portion or bearing seat of the slot 24, and the roller 32 has been swung clockwise into the outer portion of its slot 3|, the switch |2 will be locked against closure as long as the roller 32-is in position to engage the track il of slot 3| to block upward movement of the trunnion 26 which accompanies closure of the switch l2.

Theoretically, therefore, it is possible for the interlock of this invention to require substantially full opening of one switch before closure of the other switch can begin; but the operating clearances required for the trunnions and rollers in a mechanism 'of this type will permit some slight concurrent elevation of the two trunnions or rollers 25 and 26 so that closing motionof the open switch may begin slightly'be'forejthe other switch is fully open.

As indicated in Fig. 8, the substantiallyarcuate slots 30 and 3| in a sense are continuations rrespectively of the slots 24 and 23 so that vas the movable element rocks in either direction from its neutral position, the top roller 32 may rnove freely into the outer end of the slot 3i] or 3| depending upon the direction in which the ele- `ment 22 is rocked, and without any restriction due to the swinging of either trunnion 25 or' 26 in its slot. f

Ifthe top edges or tracks 40 and 4| of the slots 3|) and 3| followed concentrically the arswitch could rbegin,at least to the extent that control.

operating clearances would permit such close In other words, the bottom trunnion 25 or 26' aboutwhich the movable element rocked during opening of the closed switch could not leave its neutral position until the other Vtrunnion had been returned to its neutral or fulcruming position.

However, a desirable result is achieved by hav- `trunnions 25 and ing the top edges or tracks 4I) and .4I ofthe-slots 30-3I recede from the arcuate eenterqlines,,E and F of their respective slots as these edges ap- .proach each other.' By such recession ofthe tracks 40 and 4| declivities are provided along which the roller 32 may lrun more easily during rocking movement interlock in either direction toward the neutral position thereof, under the influence of the opening switch. Such recession of the edges ortracks 40 and 4I of course also increases slightly'the extent of the permitted or possible simultaneous elevation of the trunnions 25 andZB and consequently the switch contaotors or other members controlled by the interlock. However, it will be appreciated that the normal clearance for.the 26 in their slots 23 and :24 is ample to accommodate simultaneous upward travel of the trunnions the extent necessary to bring the top roller 32 into engagement with either track 40 or 4I or the junction of the dvergent portions of the tracks, before the trunnions can engage the outer side edges of their slots and become wedged therein.

Figure 8 shows the three rollers 25, 26 and 32 in four diierent positions, designated A, B, C and D, but does not attempt to show the necessary working clearances for the lrollers in their slots. This diagram should be considered in conjunction with Figure 9 wherein the extent ofthe opening and closing movement of the switches is illustrated.

In the full line positions A of the rollers shown in Figure 8 the movable element of the interlock is in the lockout position it occupies when the contacter of switch II is in its raised or closed position, and the contactor of switch I2 is in its ylowermost or open position. In this position of the parts, the top roller 32 is in the narrow end of its slot 3|, nearly directly abovethe fulcruming trunnion 26, so that the upper vedge or track 4| of the slot 3| precludes upward vmove- `ment of the roller 32 and trunnion 26 beyond the extent permitted by the working clearancefor the roller 32 in the narrow end of its slot 3 I and the switch I2 is eiectively locked out. I

Assuming now that the solenoid of switch I2 is energized just before the solenoid of switch I I is deenergized, the roller 32 is brought against the track portion provided by the edge 4| .of its.

slot 3| to block closing of the switch I2. This blocking, i. e., lock-out of switch I2, obtains until the solenoid of switch I I is deenergized and the weight of its contactor then swings the movable element in the counter-*clockwise direction far enough to carry the roller 32 oil" the track portion 4| and onto track portion 40. At this instant, the closing motion of switch I2 begins.-

During such changeover of the switch positions the travel of roller 32 along the declivity provided by the track portion 4| of slot 3| allows the fulcruming roller 2S to rise slightly off of its seat as a result of energization of the solenoid -of switch |2. During this time the roller 26 moves, for instance, from its position A to its position B. This distance A-B represents the maximum irecession of the edges or track portions 40 and 4| from concentricity with the arcs E and F. ,i

As the fulcruming roller 26 moves from A -B the roller 25 travels down the much greater distance A B as shown at the left in Figure 8 and the roller 32 moves to its position B- which-,is ,directly at the apex formed by the meeting track forming top edges 4G and 4| of the slots 30 andfBI.

lWith continued counterclockwise rocking' of of the movable element ointhe contactor of the switch I2. vsents the relative movement Hopen positions.

,thatthis *invention .,pecially well adapted for use with -a pair of com- .panion electro-magnetically actuated switches rmounting the interlock in xed -,themovable element from the B positions vof the rollers, the rol1er' 25 becomes the fulcruming roller .even though it has not reached the bottom of its slot 23, and the rollers 26, 32 and Hfully open position, During this changeover, it

is noteworthy `that Athe roller 32fengages continuously with the track provided bythe edges fil vand 40 of the slots-3| and 30, respectively, to assure smooth and quietoperation of the interlock. 1

In the diagram shown in Figur-e 9 theordinates indicate the travel of the contactor of the switch I I whilethe abscissas indicate the travel of the The curve G reprey ofthe contaotors as controlled by the interlock, the operation of -which is diagrammatically illustrated Ain Figure 8. The point B represents the travel whichzboth contaotors may have simultaneously from-their The dotted line H represents the motion of` similar contaotors underthe control of an ordinary rocker-type interlock.

-Not only is the interlock of this invention especially well suited for interlocking two electro-magnetically operated switches, but the length of the slots l2.3, 24, 30 and 3| in thesta- -tionary element 2| enables the interlock to 1 b e used with companion switches having vclosure `strokes varying in length,l for-example, lfrom 1%." to T95?. lFor the same reason the interlock is not restricted to use with aV pair of companion .switches both of which have closing strokes of the same length. One of the companion switches .may, for example, have a closing stroke of while the closing stroke of therother switch may be any length from f3/" to T93".

VFrom the foregoing description taken in conv,nection with the accompanying drawings it will be readily apparent to those skilled in the art provides an interlock -essince it can be applied without change to switches arranged side-by-side or in tandem one above the other and 'in either case enables maximum lsafe approach to the optimum condition at which full and complete opening of the closed switch must take place before closure of the open switch can begin. It will also be evident that the interlock of this invention, though especially well suited for use with electric switches, is not limited thereto but .also may be used to control the motion of other ycompanion -instrumentalities or movable members wherein simultaneous operation in one direction is to be precluded.

What I claim as my invention is:

1. An interlock for preventing simultaneous operation of a pair of independent electro'- magnetic switches by requiring substantially complete opening of a closed switch beforelcloing: cooperating movable and. stationary elements; means on the stationary element for relation to two switches to be interlocked; pivot forming parts on said'elements cooperating with one another toprovide spaced transient pivotal connections between said elements about either of which the movable element may .be rocked from a neutral position to one of two lock-out positions; cooperat'ing means on said elements separate from the pivot forming parts :thereon for constraining f aereas@ the movablelement when in either of its lockout positions t retrograde rocking movement toward its neutral position, said cooperating means comprising a roller on one of the elements i and a track on the other of saidelements positioned to be engaged by theroller upon rocking of themovable element about either pivotalconnection to a lock-out position to preclude allbut returning motion of the movable element to a neutral position before it can be rocked aboutthe other of its pivotal connections;. and means ,on the movable element: providing for connecting the same with eachl oi two switches to be interlocked.

v2. In a device for preventing the simultaneous operation -oi two movable members: a rocker member constrained to movement substantially in a yfixed plane; three rollerslmounted on the rocker member at thepoints of a triangle; a stationaryimember overlying the rocker member, said stationary memberfhaving spaced bearing seats,- cooperable `with two of the rollers and track means thereonwcoacting with the. third roller and disposed to constrain the rocker member substantially to rocking motion to eitherl of two dened lock-out positions about a fulcrurn provided lby the engagement of either oisaid two rollers `initsbearingseat and to constrain the rocker member to retrograde 'swinging movement'to return one oi said two rollers to fulcruming position when the rocker member has been rocked about ythe other of said two roll ers; and means Ourthe-rocker member providing for connecting the same with two movablemembers to have motion imparted to the rocker niember thereby, so that. movement of. either movable member in onedirectionrocks the rocker member about one of said two'rollers thereof` to a position blocking movement of the other movable member in one-direction. r

`3. A mechanical interlock of the character described comprising; a stationary plate cut-out to provide two arcuate converging slots arranged symmetrically about an axis passing longitudinally through thestationaryplate, the divergent ends of said slots -terminatingion a line substan-A tially normal to said axis and the radii of the arcs donned by said slots being substantially equal to the distance ybetween their divergent ends, the center lines of said slotsvintersecting 10 ing with said stationary element and connectible with parts to be interlocked; alternate transient pivotal connections between said yelen'ients including a pair of spaced aparttrunnions on one of theA elements f cooperable with bearingsurf aces on the other element to denne vfulcrurns about either of which the movable element risviree to rockto alock-out position; and a third connection betweensaid stationary andmovable `telev ,ments including a roller on one of said elements and track means on the other 0i said elements cooperable with said roller to limit translatory motion of the movable element inthe Idirection on said axis at a point substantially equispaced from the divergent ends of the slots, said stationary plate also being cut out to provide two other substantially arcuate slots joined with each other at the point of intersection of the center lines of the rst two slots and having their center lines substantially coinciding with those of said first two slots; a rocker plate overlying the stationary plate;v three rollers mounted on the rocker plate at equispaced points thereon, two of which rollers ride in the rst two designated slots and seat in the divergent ends thereof to provide alternate transient pivots about which the rocker plate may fulcrum, while the third roller rides in either of said other two connected slots to guide the rocking motion ofthe rocker plate and constrain the same to retrograde swinging movement to return one of said two rollers to fulcruming position when therocker member has been rocked about the other of said two rollers; and means on said rocker plate at opposite sides of said axis for connecting the same to two movable members to be interlocked. f n

4. In an interlock of the character described: a stationary element; a movable element coactto effect simultaneous disengagement vofsaid trunnions from their bearing seats, said third connection constraining the movable velmelflt to rock first in one direction to alockout position .and then in theopposite direction aboutl one ofv its fulcrums; before rocking of the movable element about the other V4of itsfulcrums'to the other lock-out position is possible. 5 The interlockset forthmin `claim-L4 jfurther characterized ,bythe provision ofmeans onrsaid othergelement engageable vby the Vtrunnions to precludeshiitingof the movable element in the directionoi a line the movable element.

6. The interlockset said roller and the two forth inclaim ll wherein trunnions arecarried by the movable element, and the track means and" bearing seats are on the stationary element; and wherein saidy track means faces. the trunnions and has portions lying substantially erosswise ci the direction in which the lattermove ofi?` of their bearinglseats, rocking Vof (the movable' element about-.one of, the trunnions` carryingy the roller into: engagement-with the trackportion facing the `fulcruming trunnion to block motionthere-l of oli of itsseat. 1 .t

7. The interlock set forth in claim 6 wherein said track portions are divergent and Atheijunc-4 tion'therebetween is opposite andspaced afslight distance from the periphery of said-roller 4.when both trunnionsfare engaged with their fbearing seats to allow .a'limited vdegree of translatorymoe tion ofthe movable element, in the direction to carry its trunnions simultaneously oi of their bearing seats.

8. A mechanical interlock for preventing concurrent closure of two switches, comprising: a movable element; means constraining said movable element to motion in a defined plane; a pair of spaced apart connectors on said movable element substantially equispaced at opposite sides of a median plane perpendicular to the plane of motion of the movable element, said connectors providing for the connection of the movable element to the movable contactors of the switches to be interlocked and for the application of forces to the movable element, by closure of the switches, rln a common direction along lines substantially parallel to said median plane, whereby the application of such force to one of the rconnectors by closure of its associated switch effects tilting motion of the movable element in one direction out of a neutral position to a lock-out position preventing closure of the other switch, and the application of such force to the other of said connectors by closure of its associated switch effects tilting motion of the movable element in the opposite direction out of a neutral position to a lock-out position preventingclosure of the first designated switch; a pair of joining angularly disposed stationary cam tracks facing in the direction from which force is applied to.

joining the two pivot axesof said connectors duringclosure of' either switch with the apex definedby the junction of said trackslyingon saidmedian plane when themovable element is in itsneutral position and with the tracks extending to opposite sides of said median pla-ne toward the linesalong whichv force is applied tothe connectors and lying substantially crosswise of said lines with one track opposite each connector; and a roller on the movable element cooperableY with said camV tracks and positionedv between the tracks and said connectors with' its axis normal tothe plane of motion of the movableelement and substantially in said media-n plane so that in the neutral position ofthe movable element the roller isopposite the apex at the yjunction ofr said tracks so that the force applied to either connectoras-a result of closure of itsI associated switch tilts-the movable element to a lock-out position in which the roller is interposed between the other connector and the stationary cam track opposite the same and substantially in line with-the force which would-be applied to said other connectorV by a tendency-to close its associated switch to thereby blockA` concurrent closure of bothV switches.

9. A mechanical interlockl for preventing concurrent closure of two switches; comprising: a movable element; .means constrainingsaid movablevelelnentto motion ina defined plane; a pair of spaced` apart connectorson said movable element.substantiallyI equispaced at opposite sides offa-medianplane perpendicularto the plane of motion of Y the movable element; said connectors providing for the. connection of the movable element to themovablecontactors of the switchesto beinterlocked andifor theapplication of forces to thamovable-element, by: closure of the-switches, in a common direction along lines substantially parallel to said median plane, Wherebyfthe application offsuch force-to oneofthe connectors byfclosure. of' its associated switch effects tilting motionl of the movable element in one directionfout ofl aneutralpositionto a lock-out positionpreventing closure of the other-switch. and theapplication of 'such force to the other'ofy said connectors by closure*` of-Iits associated switch ef- 12 fects tilting motion ofthe movable element in the oppositev direction out of a neutral position to a lock-outposition preventing closure of the rst desigr'ia-tedV switch; a stationary cam track facing and substantiallyinsaid median plane so that-in the neutral. position ofzthe. movable element the roller isoppositethe mid-portionofthe cam track so that the force applied to either connectorsas a result of" closure. of its' associated switch .tilts thev movable element. to alock-out positionin which the roller is interposed between the other connector vand thev portion of. thestationary cam track opposite. thereto. andsubstantially in. line with. the force. which4 wouldA be applied to said other connector by a tendency to close its asso;- cated. switch to thereby block concurrent closure of both switches.

JOSEF BIERENFELD; f

REFERENCES CITED Theiollowing referencesvare of'record in the le of this patent: 

